The present invention relates to a process for producing a substrate for photosensitive drum a substrate which is suitable for the production of a photosensitive drum being free from the occurrence of interference fringes and has fine streaks uniformly formed on the surface thereof by machining without burrs, and the substrate capable of producing a higher-quality photosensitive drum. More particularly, the present invention relates to a process for producing a substrate which is suitable for the production of a photosensitive drum being free from the occurrence of interference fringes and has fine streaks uniformly formed on the surface thereof by machining without burrs, and the substrate capable of producing a higher-quality photosensitive drum.
As is well known in the art, a photosensitive drum (cylindrical electrophotographic photosensitive member) includes a cylinder-shaped substrate (photosensitive drum substrate) made of aluminum or an aluminum alloy, and a photosensitive film as a photosensitive layer formed on the surface of the substrate. The substrate for such a photosensitive drum has been generally produced by machining the surface of a drawn stock tube to obtain a drum body having a high-precision shape and then subjecting the surface of the thus obtained drum body to surface-smoothening treatments (such as mirror finishing or predetermined surface-roughening treatment) by precision-machining using a diamond turning tool or the like.
In FIG. 5, there is schematically shown a structure of a cutting edge of a diamond turning tool used for the production of conventional photosensitive drum substrates as viewed from a front flank side of a tip of the turning tool. FIGS. 6 and 7 are enlarged photographs each showing a surface condition of a substrate for photosensitive drum which is machined by the conventional diamond turning tool. Namely, in the production of the conventional substrate for photosensitive drum, the turning tool having the cutting edge shown in FIG. 5 is used so as to smoothen the surface of the substrate as a whole as shown in FIGS. 6 and 7.
For example, in Japanese Patent Application Laid-Open (KOKAI) No. 6-194857(1994), there is described a process for producing a substrate for photosensitive drum in which the surface of the substrate is finished into a surface roughness of about 0.2 to 1 xcexcm using a diamond turning tool. The diamond turning tool used in the above process includes a major cutting edge constituted by a rake face and a side flank thereof, and a minor cutting edge formed by the intersection of the rake face and a front flank thereof, and the major and minor cutting edges are constituted by many particles of diamond. Further, the front flank thereof is provided with a polished surface having no polishing scores. Also, a peripheral edge of the minor cutting edge is finished by grinding with whetstone for removing large irregularities of diamond particles therefrom.
On the other hand, in order to enhance a quality of the photosensitive drum, it is extremely important that the substrate therefor has a smooth surface. However, it is known that when the surface smoothness of the substrate is too high, interference fringes (moire) are caused on a photosensitive layer formed on the substrate when scanning the surface of the photosensitive drum by a laser beam. For this reason, there have been studied such a method of machining the substrate using a turning tool having a cutting edge with saw-like portion (irregularity portion) for forming fine streaks on the surface thereof, thereby causing irregular reflection of light on the surface of the photosensitive layer of the photosensitive drum to inhibit the occurrence of the interference fringes thereon.
Meanwhile, in such a production method, fine split burrs which are actually invisible by eyes, tend to be formed on the surface of the machined substrate as shown in FIGS. 6 and 7, which burrs are located at portions surrounded by circles. Also, even if the substrate is machined by the above-described turning tool having many particles of diamond cutting edge with saw-like portion to form fine streaks on the surface thereof, the non-uniformity of depths of the respective streaks is caused. The formation of such non-uniform streaks and burrs upon machining are considered to be problems peculiar to turning tools made of many particles of diamond.
Namely, as shown in FIG. 5, the above-described many particles of diamond cutting edge is formed by subjecting diamond particles to sintering treatment and then flattening the surface of the obtained product by polishing. For this reason, the diamond particles exposed on the surface of the cutting edge are actually not only different in size from each other but also irregularly oriented. Accordingly, even though the many particles of diamond cutting edge is provided therealong with regular irregularities, the shape of the cutting edge is non-uniform, and especially the depths of concaves between the diamond particles forming the cutting edge become uneven. This sometimes results in failure to sufficiently inhibit the occurrence of interference fringes on the obtained photosensitive drum. In particular, the burrs on the surface of the substrate cause significant problems upon the formation of a photosensitive layer thereon, which leads to defective images caused by the photosensitive drum.
The present invention has been made in view of the above problems. It is an object of the present invention to provide a process for producing a substrate suitable for the production of a photosensitive drum being free from the occurrence of interference fringes thereon, which is capable of forming uniform fine streaks on the surface thereof without burrs when the surface of a stock tube is surface-smoothened by machining.
It is another object of the present invention to provide a substrate for photosensitive drum which has uniform streaks on the surface thereof without burrs, and is capable of producing a photosensitive drum having a higher quality.
To accomplish the aims, in a first aspect of the present invention, there is provided a process for producing a substrate for a photosensitive drum, which comprises machining a surface of a cylindrical stock tube by a turning tool in order to form a cylindrical substrate having a surface roughness of 0.5 to 5 xcexcm and having, on the surface thereof, streaks extending in the approximately circumferential direction thereof, the said turning tool being constituted by monocrystalline diamond and having a cutting edge provided with a saw-like portion (irregularity portion) along an effective cutting length thereof.